Tvheadend

So when you view a programme synopsis in the web interface, the channel icon is displayed in the top right of the synopsis window? If you are getting icons (as per my screenshot) then there's no reason why they wouldn't be offered up to HTSP clients. Try the following;

In Kodi - have you tried clearing the EPG cache from Settings > TV > General > Clear data and letting it pull down the new data from TVH?

TVHClient has always been a bit flaky with icons for me - it seems to take ages to recache the data and sometimes deleting the configuration and re-adding it was the only way to get it to pull down the icons.

Yes, I get the icon in the synopsis in the right corner - like in your screenshot.

I tried the clearing of the EPG cache. But it did not help.
Maybe I have to mention I did the test with MRMC on ATV4 and iPad. So, it's the Kodi branch. However, I will test it again with Kodi on Windows.

I removed the TVHClient App and installed it again. But it did not help.

Can I log/debug somehow - to see if the clients receive the icons or not?

I solved the problem.
Using http://... for the icon path works.
file:///... is working only in the web-interface.
Why? I don't know. The trace/debug log does not help.

That is really random, I've just double-checked mine and I am using file:/// for both channel icons and picons and I get icons in the web UI, Kodi and TVH client on my iPhone.

Oh well, least you got them working one way or another

Just while I'm thinking about it, could it be a permissions issue? I've got my picons and icons folder permissions set to 777 so that I can update them by dragging files into shares rather than messing around logging in.

I created a new shared folder with 777 permissions for the tvheadend-test user.
file:/// is not working.